Astronomy Dictionary
A wonderful illustrated dictionary of Astronomy terms can be found here.
February 27, 2009
This month’s night sky
Each month the Sydney Observatory posts an .mp3 of the night sky.
You can get that .mp3 from here.
Stellarium
Stellarium is free software program for exploring the night sky.
Download Stellarium from here.
Hertzsprung-Russel diagram
The Hertzsprung-Russel diagram sorts stars by their absolute magnitude and surface temperature colour.
The majority of stars, including our Sun, are formed along a region called the Main Sequence. main Sequence stars vary widely in effective temperature but the hotter they are, the more luminous they are, hence the main sequence tends to follow a band goiung from the bottom right o fthe diagram to thetop left.
These stars are fusing hydrogen to helium in their cores. Stars spend the bulk of their existence as main sequence stars. Other major groups of stars found on the H-R diagram are the giants and supergiants; luminous stars that have evolved off the main sequence, and white dwarfs. How to read an H-R diagram reading-h-r1.
A question of distance
The estimated distances from Earth to some of the stars and galaxies in our universe are listed below. How long would it take to reach each of them travelling at the speed of light. (300 000 km/sec).
The light from the Sun takes just over 8 minutes to reach Earth.
| Sun | Our own star | 1.5 x 108 km |
| Proxima Centauri | The closest star to Earth | 4.0 x 1013 km |
| Centre of Milky Way | Our own galaxy | 2.5 x 1017 km |
| Magellanic Clouds | One of the closest galaxies | 1.5 x 1018 km |
| Andromeda galaxy | One of the closest galaxies | 1.4 x 1019 km |
| Quasars | Very distant objects | 1.4 x 1023 km |
How long would it take to reach each of them travelling at the speed of light. (300 000 km/sec).
